UAW spokesperson Christine Moroski said Tuesday that of the 40 plants in the U.S. and Canada 25 are unionized.

Asked to respond for this story, the company said, "Flex-N-Gate associates receive competitive wages, enjoy quality growth opportunities and benefit from our ongoing commitment to safe working conditions.

"The vast majority of Flex-N-Gate associates are happy with their employment."

The UAW says many Salem plant employees have worked there for 10 to 20 years and "still only earn around $10 an hour."

"Workers want to organize in order to improve pay and working conditions, and to work with the company to make it more successful," Moroski said adding the rally is to inform the public.

"Traditional views of jobs in the auto are good but the auto parts sector pays poverty-level wages," she said.

"Many employees are on food stamps. This is a highly profitable company and can afford to pay higher wages."

She added, "Certainly we don't think $10 is a living wage."

With healthcare costs around $200 a month, she said many can't afford it and live without it.

The demonstrations are aimed at shining a light on the company's treatment of workers at its non-union facilities and to show support for workers bargaining new contracts, the UAW said, adding it represents workers at six facilities owned by Flex-N-Gate.

Workers at several plants in Indiana, Illinois, Michigan, Ohio and Texas, have been illegally fired or disciplined for attempting to form a union, according to the National Labor Relations Board, the UAW said.

The Ventra plant employs approximately 450 hourly people and about half are women, Gearhart said adding there are issues regarding respect, treatment of workers, favoritism, wage and raise disparities and safety concerns.

There is "no structured way" these are handled, he said.

"Workers just want a voice in the things that matter to them and to make the company better in Salem," he said.

He expects support from nearby UAW locals and other unions that will assemble off the company property on Pennsylvania Avenue.

UAW members at Flex-N-Gate union plants in Warren, Mich., and Belvidere, Ill., are currently trying to bargain new contracts.

At both facilities workers voted overwhelmingly to strike if necessary to achieve a fair contract, the UAW said.